Shrink debuginfod volume from 100G to 25G

This hasn't seen much growth in the past two months and is chilling
around 13G. We can easily bump it once we have more debug packages.

tf-stage1/archlinux.tf

@@ -503,6 +503,6 @@ resource "hcloud_volume" "monitoring" {
 
 resource "hcloud_volume" "debuginfod" {
   name      = "debuginfod"
-  size      = 100
+  size      = 25
   server_id = hcloud_server.machine["debuginfod.archlinux.org"].id
 }